1. Field of the Invention
The present invention relates to a projection TV receiver (hereinafter referred to as a projection TV) having semiconductor circuits that are constituted of thin-film transistors using a thin-film semiconductor.
2. Description of the Related Art
In recent years, the technology of constructing semiconductor circuits by forming TFTs on a substrate having an insulating surface has made a rapid progress. A typical example of such semiconductor circuits is an electro-optical device such as an active matrix liquid crystal display device.
The active matrix liquid crystal display device is a monolithic display device in which a pixel matrix circuit and driver circuits are formed on the same substrate. Further, the system-on-panel which incorporates not only a pixel matrix circuit and driver circuits but also a memory circuit and logic circuits such as a clock generation circuit is now being developed.
With increased demand for electronic devices that utilize such display devices, keen competition for development of such electronic devices is now being made. A typical example of those electronic devices is a projector.
The projector is a device for applying strong light emitted from a backlight to a liquid crystal display device and projecting an image formed by the pixel matrix circuit of the liquid crystal display device onto a large-size screen.
The projector is generally classified into two types. The type in which an image is projected onto a rectangular screen whose sides measure several meters from the front side is called a front projector (or a front projection TV). The type in which an image is projected onto a screen having a diagonal size of tens of inches from the back side is called a rear projector (or a rear projection TV).
Particularly in recent years, with the scheduled full digitization of ground-wave broadcasts, the rear projection TV has becomes the most promising candidate for future TVs for home use. This is based on a view that the rear projection TV will be advantageous over the CRT-type TV in terms of resolution, compactness, weight (lighter weight is preferable), set productivity, and power consumption (lower power consumption is preferable).
In view of the above-mentioned demand, an object of the present invention is to provide a projection TV that is highly reliable and easy to maintain.
According to a first aspect of the invention, there is provided a projection TV having at least an optical system and a liquid crystal module, wherein thin-film transistors constituting the liquid crystal module have a channel forming region that is a crystal structural body in which a plurality of rod-like or flat-rod-like crystals are arranged approximately parallel with each other in a particular direction; and wherein the thin-film transistors have an operation temperature of 80xc2x0 C.-250xc2x0 C.
According to a second aspect of the invention, there is provided a projection TV having at least an optical system and a liquid crystal module, wherein thin-film transistors constituting the liquid crystal module have a channel forming region that is a crystal structural body in which a plurality of rod-like or flat-rod-like crystals are arranged approximately parallel with each other in a particular direction and crystal lattices are continuous at most of grain boundaries; and wherein the thin-film transistors have an operation temperature of 80xc2x0 C.-250xc2x0 C.
The most important features of the invention are that the kink effect (the phenomenon that the operation is rendered out of control owing to hot carrier injection or the like) in a thin-film transistor is prevented or inhibited in a state that it is operating, and that a liquid crystal module that is constructed by using such thin-film transistors is applied to a projection TV.
The thin-film transistor utilized in the invention has a feature that the kink effect is prevented in a state that the thin-film transistor is operating in such a manner that charge that is captured in a gate insulating film by hot carrier injection or the like during operation is released by self-heating that is caused by the operation.
Because of the unique feature that the resistance to deterioration is increased by heating, this type of thin-film transistor is considered a switching element that is most suitable for use in a projection TV which is prone to accumulate inside heat that is generated by strong light coming from a backlight or by self-heating.